The present invention relates to a monitoring and diagnosing method and system which monitor and diagnose the condition and operation of plants such as nuclear power plants and thermoelectric power plants.
There are various kinds of plants for producing energy and reaction products, e.g., nuclear power plants using boiling water reactors and pressurized water reactors, thermoelectric power plants in which petroleum, coal, natural gas, etc. are burnt, and chemical plants for producing and refining petrochemicals such as ethylene (hereinafter these different types of plants referred to simply together as plants). In these plants, objects to be controlled are subject to a wide temperature range from low to high temperatures, and phase of the objects is changed from liquid to gas phase and, in some cases, even to solid phase at different locations within each plant.
For each condition of start-up, steady operation and shut-down of a plant, the temperature and phase of the controlled object are variously changed at different locations within the plant. Generally, the operation of a plant is controlled by a computer. In order to achieve optimum operation efficiency of the plant or smooth start-up and shut-down thereof, various variables in the plant such as pressure and temperature are measured every moment, and the plant is operated under control of the computer so that the various variables are optimized.
FIG. 16 is a schematic structural view of main apparatus and equipment of a nuclear power plant using a boiling water reactor.
In FIG. 16, reactor internals such as a fuel assembly and a jet pump 22 are disposed in a pressure vessel 17. The pressure vessel 17 is housed in a reactor containment vessel 16 along with other main apparatus and equipment for controlling and cooling the reactor, such as a control rod drive unit and a recirculation pump motor 29.
During normal operation, control rods are withdrawn from a core 23 so that nuclear fission of uranium as the fuel reaches critical mass to produce heat. The jet pump 22 is driven by the recirculation pump motor 29 disposed in a recirculation loop 26, whereby cooling water is circulated to remove the heat generated by the nuclear fission from the core. Then, high-pressure steam at 280.degree. C. and 6.9 MPa is produced and supplied to a turbine through a main steam line 24 for driving the turbine to thereby generate electricity. The steam is condensed by a condenser into water that is returned to the reactor through a feed-water line 25. During the operation, nitrogen gas is filled into the reactor containment vessel 16 for the purpose of noncombustibility.
If any abnormality should occur in the reactor system, the reactor is shut down and the reactor system is isolated within the reactor containment vessel 16 by operating main steam isolation valves installed inside and outside of the reactor containment vessel 16. Also, any overpressure in the reactor is relieved through a safety release valve 18, and safety equipment such as an emergency core cooling system is operated.
Denoted by reference numeral 21 is a shroud disposed to surround the core 23. Further, 20 is a steamy water separator, 37 is a dry well, and 19 is a steam drier. The steam water separator 20 serves to remove condensed water, and the dry well 37 serves to release a steam/water mixture in the event of loss-of-a-coolant accident. 28 is a coolant purifying pump which supplies a coolant to the feed-water line 25 through a filter/demineralizer 27. 15 is a reactor containment vessel spray for scattering cooling water, and 30 is a similar spray. 31 is a turbine pump for cooling in the event of isolation. In case of the reactor becoming isolated from the turbine system, the pump 31 serves to cool the reactor.
Further, 32 is a residual heat removal unit and 36 is a residual heat removal pump, the heat exchanger 32 and the pump 36 serving to remove the decay heat after shut-down of the reactor. 33 is a high-pressure core spray pump, 34 is a low-pressure core spray pump, and 35 is a pressure suppression chamber.
In the above-described nuclear power plant, the operation of the nuclear power plant is periodically shut down and the main equipment and apparatus are dismantled and disassembled to check for the presence or absence of an abnormality and any degree of deterioration for the purpose of ensuring reliability of the nuclear power plant. Also, the presence or absence of an abnormality is checked in a nondestructive manner and, if any abnormality is found, the relevant apparatus and/or parts are repaired or replaced with new ones, thereby ensuring reliability in the operation of the nuclear power plant. In the nuclear power plant during the operation, the operating condition represented by parameters primarily related to the reactor, such as power, temperature, pressure and flow rate of circulating water, are monitored at all times. Based on the monitored results, it is confirmed that the operating condition of the nuclear power plant is normal. For each of the pumps and other main components, such parameters as rotational speed, delivery pressure, temperature and flow rate are monitored to confirm the operating condition thereof. In addition, not only the vibrations and temperature of each apparatus, but also leaked steam, water, radioactive rays, etc. around the apparatus are monitored to confirm that the environment surrounding the apparatus is normal. Thus, the presence or absence of an abnormality in the operation of the nuclear power plant is always confirmed.
For periodic inspection of the equipment and apparatus, the advanced checking operation is promptly performed by expert workers having advanced skills in conformity with legal check items. FIGS. 17A-17D is a table showing a summary of methods for diagnosing the main apparatus and equipment, and FIG. 18 is a table of main sensors for diagnosis of the main apparatus and equipment (reference: "Equipment Diagnosing System of Nuclear Power Plants", Uchida and three others, Sensor Technology, October 1992, pp. 84-89).
As the prior art relating to monitoring and diagnosis of plants and apparatus, there are known, for example, patent laid-open publications concerned with apparatus (JP, A, 58-134312 and JP, A, 3-220498) and with plants (JP, A, 58-215593, JP, A, 63-313208 and JP, A, 63-241876). In these publications, a prediction model for the operation of an apparatus or plant to be monitored is utilized to detect an abnormality from the difference between the model and actually observed results.